In recent years, microscopes used as fluorescent microscopes are widely used not only for microregion observation but also for macroregion observation. Since such microscopes require bright, uniform illumination, near coaxial epi-illumination has come to be used more often, replacing conventional oblique illumination and coaxial epi-illumination.
FIG. 12 is a view showing an example of a stereoscopic microscope as a conventional fluorescent microscope (refer to, for example, Patent Document 1). In this case, a frame 1 is placed on a desk (not shown). On the frame 1 is a specimen 2 mounted as a sample to be observed. The frame 1 has a footplate 101 and a post 102, or a support member, disposed upright on the footplate 101. The post 102 has a focusing unit 3 as a focusing unit. The focusing unit 3 includes a fixed member 301 fixed to the post 102, and a movable member 302 movable relative to the fixed member 301. The movable member 302 is provided with a focusing handle 303. The focusing handle 303 is used for focusing, and moves the movable member 302 vertically along the post 102 according to the rotation of the handle 303 by means of a focusing mechanism, which has a raising/lowering mechanism formed from a rack and pinion (not shown).
Disposed on the movable member 302 is a light-projecting tube 400. Also, disposed at the leading end of the light-projecting tube 400 is a zoom mirror 500 serving as an observing optical unit that has a zoom optical system having variable zoom power. The light-projecting tube 400 has an upper tube 400a and a lower tube 400c disposed parallel to the footplate 101, and a space 400b disposed between the movable member 302 of the focusing unit 3 and the zoom mirror 500. The light-emitting tube 400 is provided with an illuminating unit 7 serving as a light source unit. Illuminating light, serving as excitation light emitted from the illuminating unit 7 is guided to an illuminating optical system 401a in the light-projecting tube 400, and then into the space 400b via an excitation filter 9a. An optical axis L1 of the illuminating light introduced via the illuminating optical system 401a is located in the space 400b. Disposed along the optical axis L1 is an illuminating optical system 401b used to relay the illuminating light further. The light transmitted through the illuminating optical system 401b is reflected by reflecting mirrors 402 and 403. Subsequently, the light is thrown onto the specimen 2 through an objective lens 6 (described below) in near coaxial epi-illumination.
An objective lens 6 is attached to the underside of the lower tube 400c. The objective lens 6 can be focused on the specimen 2 by changing the distance relative to the specimen 2 by moving the lens in the direction of the optical axis of light away from the specimen 2 (i.e., in the direction of an optical axis of observation L2 coinciding with the optical axis of the objective lens 6) by the vertical movement of the light-projecting tube 400 according to the operation of the focusing unit 3. The zoom mirror 500 is disposed in a space between the upper tube 400a and the lower tube 400c. The zoom mirror 500 has a zoom optical system 501 and a zoom handle 502. The zoom optical system 501 is disposed along the optical axis of observation L2, and allows zoom observation of variable power by its being subject to a zoom-power-varying operation according to the rotating operation of the zoom handle 502. Within the leading end of the upper tube 400a is an absorption filter 9b. On this leading end is an imaging optical unit 8 with an imaging lens (not shown) and an eyepiece 801, through which the visual observation of an observation image of the specimen 2 formed by condensing light via the objective lens 6 is possible. In addition, the excitation filter 9a and the absorption filter 9b are disposed in their respective specific positions on a turret 9c disposed in a filter unit 9. The filters 9a and 9b are freely replaceable with other excitation and absorption filters of different optical characteristics.
In such a stereoscopic microscope, the space 400b of the light-projecting tube 400 is defined between the movable member 302 of the focusing unit 3 and the zoom mirror 500. Illuminating light as excitation light from the illuminating unit 7 is transmitted through the illuminating optical system 401b in the space 400b, then passed through the objective lens 6 by the reflecting mirrors 402 and 403, and then thrown onto the specimen 2 via the objective lens 6. Fluorescence emitted from the specimen 2 as a result of the excitation light thrown thereon is passed along the optical axis of observation L2 of the zoom mirror 500 from the objective lens 6, and then guided to the imaging optical unit 8 via the absorption filter 9b, and observed through the eyepiece 801.
On the other hand, Patent Document 2 discloses a fluorescent microscope, the configuration of which is such that the space of a light-projecting tube is defined between a focusing unit and an observing unit, composed of an objective lens and a zoom-power-varying optical system, and an illuminating optical system with a prism is disposed in this space. In this case, light is obliquely thrown onto the specimen from the light-projecting tube by the illuminating optical system and the prism corresponding to the magnification.
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-166214
Patent Document 2: Japanese Patent Application Laid-Open No. 2002-098899